Gasp!
My fourth grade teacher might've been right after all - chewing gum in
class may actually be bad for you:

... scientists at Cardiff University in Wales now find chewing
gum can impair classic tests of short-term memory — recalling
lists of words and numbers in the order in which they were seen or heard.
They also saw that people were less able to spot missing items in lists
— for instance, that '7' was missing the list '28149365' taken
from the digit set 1 to 9.